Telephone broadcast system



Sept. 19, 1944. c. s. RHOADS TELEPHONE BROADCAST SYSTEM Filed July 28,1943 2 Sheets-Sheet l Nwmdrn N .wHm

wkomuwmmw Q 1N VEN TOR I ATTORNEY Sept. 19,1944. c. s. RH S. 7 2,3

TELEPHONE BRADCAST SYSTEM Filed July 28, 1945 2 Sheets-Sheet 2 sag m 521RM;

S54. R :gsk 2* 12 IN VEN TOR ATTORNEY 5 Zine finale] 0; Zing Switch toJubscl libel Patented Sept. 19, 1944 UNITED STATES 2,358,594 TELEPHONEBRoAneas'tr sysgl sm.

Charles Stanley Bhoads, Albany; N. Y-., assignorto American Telephoneand Telegrapheompany, a corporation of New York" Application July, 28,1943; Serial No. 496,441 7 1 This invention relates. to telephonesystems and more. particularly to telephone systems of the machineswitching type. v

In step-by-step telephone. systems; or panel telephone systems, forexample, it mayhappen that one or morecentral ofiices or one or. moregroups of trunks have been disabled .becauseof an accident oraconditiondueto war. Numerous parties may seek to establish connectionover the group orgroups of trunks-onto the disabled. o-ffice i or oficesbut may find that their connections can= not-be. completed. Under suchconditions thecalling' parties may. continually dial" the desiredparties and seek to establish connections through the disabled centralofilces or-groups of. trunks and this will result in considerabletraffic overload and block calls that could be completed. Itisproposed,therefore, to provide at a central ofiice or central ofiices notdisabledbutconnected to'the disabled central office or oflices, or to the'xgroupor groups of trunks an arrangement whereby the parties endeavoring; to.reach the disabled'ofii'ce may be notified that-their. connectionscannot be completed.

Accordingly, itis anobject of thisinvention to provide an arrangementfor connecting a telephone transmitteriata central oflice to broadcastan attendant at a. central ofiice to be. apprized of the fact that oneor more partiesare calling .a particular office-onseeki'ng connection.of any one ofzapgroup ofi-trunksand. to. enable the attendant to talk tothe various .callingpartiesiati one time. The: objectof this. inventionmay be accomplished by substituting a telephone. set for. the busy tonegenerator. at the. eleventh: step: switch of;:a step-by-step telephone.system. When this conversion is made. the telephone set may; beused forsupplying: informationto all. of the parties connectedto" all of: thefirst selectors advanced to the eleventh step atthe-centraloffice. In.that case the busy tone-will not be: furnished to the calling; partieswhen they. dialha. particulan'ofiice or a particular group: of. trunks;but instead the calling parties will beconnectedi tothe telephonesetxand'the. attendant may then talk to the calling partiesat'the same.time'and appri'ze thenrofi the conditions oftransmissi'on .orgive them.other iniormation. A similar arrangementijma-y': beganplied to panelandother types ofv telephone ,sys: tems...

Thi invention will betterunderstood .frc'm the ;more; detaileddescription: hereinafter renew; ing; when read in .connectionwithftheaccomp ying; drawings in whichFi'gureT 1 illustrates, th in.- ventionapplied to a, step-by-stepftelephonei.sys; tem and Fig; 2 illustrates.the invenjtion appnedto apanel type.of-telephone systeml R fe r a fthe? a ings, tw o a plurality of first selectors of a step-by-fsteptelephone system are shown, each 'of-whicliimayrlge used for connectingasubscriber's setsiichgas' SS1 to. ,agsucceeding selector. Onecof thesfirst Qse} leetor is shown in detailand :it'. is; conn edi by three,conductors T1, R and Srpf a; trunk 1K1 toother centralofliceeguipmentCQi 1., lector. will be used. to establishr 'a connectionbetweenthetrunk TX; and. anyone 'ofjanunlber; of other trunks suchas 'IK1'2 which comprises conductors T12, R12 andsia. .This1firsts'elect0rmay include a Strowger switch", which, as is Well lrnown, has a verticalmagnet a. rfi jease midgnet and ofi. normal contacts. VON." This switchmay. be employed, to connect the trunk conductors T1,;R1and S1associated withtrunl; to any one of tenotherlti lks such as 'IKiz in; agroupp'f trunksi'as is iwell'kriown. ."I'he ele ve enth t ew t h SW beemr 'qv d t nbly dial tone to the calling. :s bsc riber'sjset;suchjasS51 through the normal upper ontacts of the switch SW. The lowernprmalcontactsofftlie switch SW may be employed/tor applying busy tone;to the; calling subscriber's setssrjafter all of the ten trunks ataparticular'levelihavebeeh tested by the Strowger switch mechanism andfoundbusy.

When the calling. party having thetelephone set S,S1,,,for exampleremoveshis receiver from its hook, the relay A will becomeoperatedover'fa circuit whichincludes battery, the upper winding ofrelay A, the inner upper'armature. and back contact. ofrelay-D, theconductor 31 of trunk TK1, the subscribers set SS1, the; conductor Ji lof the trunk- TK1, the upper outerarmatureand back contact ofrelayD;the; lower winding-Mire; lay A, the upper normal contacts of switch SW,the primary winding of vdial tonatrans for r- -li and ground. Theclosure ofv this circuit; ser es; to supply dial tone to the callingsubscriber an pen hearin the dial tone he ,mayrthen proceedtofdial thedigits of any desired number; iThe operatioh of relay A will result intheoperatio mm B over acircuit which includes battery thegwind ing ofthe relay B3,.the .windin =.of.reIayLBL the armature and make contact ofrelay A, the lower outer armature and back contact of relay D andground. The operation of both relays IA and B prepares a circuit foroperating the vertical magnet VM of the Strowger switch, as will beexgized, the operating circuit including battery, the

windings of the vertical magnet VM and relay C, the lower armature andmake contact of relay B, the armature and back contact of relay A, thelower outer armature and back contact of relay D and ground. Theoperation of the vertical magnet VlVI raises thewiper shaft of theStrowger switchby one level, asis well'understood. Each subsequentinterruption of thecircuit between the windings of relay A 'and'thesubscribers dial set in'response to the digit dialed by the callingcontact of relay D upon the operation of relay D. The circuit foroperating relay D includes battery, the winding of relay E, the rightcontacts of the switch VON, the armature and back contact of releasemagnet RM, the winding of relay D, the lower normal contacts of switchSW, and upper outer armature and make contact of relay B and ground.Although the windings of relays D and E are connected in series witheach other. in this circuit the resistance of the winding of relay D isso high that it will prevent relay E from operating at the same time.

When relay D operates, the tip conductor T1 of trunk TK1 will beconnected through its upper outer armature and make contact to the tipconductor T12 of the trunk TK12, the ring conductor R1 of trunk TK1 willbe connected through the upper inner armature and make contact of relayparty will result infraising the wiper 'shait of the Strowger switch oneadditional level. I Y v Immediately after the' first movement of thewiper shaft of the Strowger switch, the off normal switch VON will closeits contacts and cause relay E to operate. The operating circuit forrelay E includes battery, the winding of relay E, the right contacts ofthe switch VON, the armature and make'contact of relay C, the upperarmature andmake contact of relay B and ground. Relay E will thenbelockedin its operative position, the lockingjc'ircuit' includingbattery, the winding of relay E, the right ,contacts of the switch VON,

the armature and'back contactof the release magnet RM, the outerarmature and make contact of relay E, the lower outer armature andbackcontact of relay D'and ground. Relay C willrelease soonfafter thelast interruption of the pulses of the first digit dialed by the callingsubscriber. The releaseof relay C will complete acircuit for theoperation-of the rotary magnet RM, the circuit now completed'includingbattery, the winding of the magnet RM, the inner armature and makecontact of relay E, the makebefore-break contacts of relay C, the upperarmature and make contact of relay B and ground.

The operation of the rotary magnet RM will rota't'e the wipers of theStrowger switch to the first set of bank contacts, as is wellunderstood. At the same time the operation of the rotary magnet RM will"break the locking circuit of relay-Eat the backcontact of the armatureof the magnet RM; r

The relay E will operate'if the sleeve conductor of the first set ofbank contacts is grounded as it would be if the'associated trunk werebusy,

and on the other'hand relay E will release if the sleeve conductor --ofthat trunk isu'ngrounded as it" would be if that trunk were idle. Therelay D will likewise operate'or remain unoperated, depending uponwhtherthe sle'eve'conductor of the trunk of the first set of bank contacts isfound grounded or 'ungr'ounded. If one of the trunks such as'TK iz ofthe group is idle and its sleeve conductor S12 therefore ungrounded, thesleeve conductor S12. of that trunk will be? connected to the groundedsleeve conductor S1 through the lower inner armature" and make D to thering conductor R12 of the trunk RKIZ, and the sleeve S1-will beconnected with the sleeve S12 as already noted so that both will begrounded. If the trunk, such as TKlZ, has been found busy by theStrowger switch, ground at its'sleeve conductor S12 would have beenconnected to the upper terminal'of the winding of relay. D through thelower inner armature and back contact of relay D. In that case bothterminals of the winding of relay D would be grounded and hence relay Dwould remain unoperated- Nevertheless, relay E would be operated tocause the rotary magnet RM to step the wipers to the next set of trunkcontacts.-v This rotary movement will be continued until a sleeveconductor of oneof the various trunks on the same level is foundungrounded.

When all of the ten trunks on the level correespondingto the digitdialed by the subscribers set SS1 are busy, the eleventh step switchSWbecome operated in a -well known manner anda trunk signal will betransmitted to the'calling subscriber; Thetrunk busy signal current willflow over a circuit which includes the secondary winding of. transformer.T2, the normal contacts of key K1, the upper make contacts of switchSW, the lower winding of relay A, the upper outer armature and. backcontact. of. relay D, the telephone subscribers set SSiQthe upper innerarmature and back contact-of relay. D, .the upper winding of relay 'A,battery. and ground. This is the normal circuit for trunklb'usy tone butas will be explainedhereinafter, a telephone set may be substituted forthe source ofbusy .tone to enable an attendant to broadcast'to thecallingsubscriber having the set SS1 and to other'calling subscribersconnected to'the various selectors at the office that have advanced .tothe eleventh step of the switch. a r V The release magnet RLS will beoperated after the call has been completed and the subscriber hasreturned his receiver to its switch-hook and relayD has restored tonormal. The operation of the release magnet RLS .is brought about. bythe completion of a circuit from batterypthe winding of supervisoryrelay SR, the release mags net RLS, theleft contacts of the switch VON,the lower armature and back contact of relay B; the armature and backcontact of relayA, the lower outer armature and back contact of relay Dand ground. It is noted that relays A and B become releasedimmediatelyafter relay D is operated and remain released thereafter toenable therelease magnet RLS to operate. I Whenever'all of the trunks onthe level of trunk 'I'Krz are disabled and" the sleeve conductors ofthese trunks of thatlevel have been grounded so that they will appear tobe busy, all parties calling that group of ftrunks willof course-findthem busy. But in accordance with'this invention,- tlie -attendant' mayoperate thekeyKi so that she may connect a telephone set" in-place ofthe-'busy tone source, for the'purposes alreadyreferredtohereinabove;Ifthe telephone systemis of'the common batterytype, the attendant mayalso close her key- Kz'and thereby connecta common bat tery set CBSthrough keys K2 and K1 to theupper contacts 'of-switches SW, SW1, SW2,etc. and the windings of' relays A, A1, A2, etc. The circuits will besubstantially the same-as already described'hereinabove for the returnof busy tone tothe calling'subscribers. However, other t'elephonesetssuch as SSzconnectedtofirst selectors similar to'the'one alreadydescribed will alsobe connected to the same common battery setCBSiIi'rthat case-the telephone set CBS may be used by-the'attendant fornotifying all ofthese calling subscribers simultaneously that all of thetrunks of the desired level are busy, or that the ofiice called by theseparti'e's'is disabled, or the attendant may furnish them otherinformation of importance to them. This is one of the features of theinvention. The battery connected to the upper winding of relay A may inthat case supply current to the windings of all of the various A relaysof the other first selectors in parallel. With this arrangement asubstantial increase in the number of subscribers sets connected inparallel with the common battery set CBS will increase the current flowthrough the transmitter of the common battery set which will compensatefor the added load of the listeners and permit the attendant to speak tothe various calling parties at the same time, the transmission levelremaining high under these conditions. This feature has already beentried out in the plant and all of the parties were found capable ofreceiving the attendants message at a good transmission level, and it isnot possible for one calling subscriber to talk to another whenconnected to this circuit.

A magnetoset such as MS maybe connected to the switches SW, SW1, SW2,etc., and to the windings of relays A, A1, A2, etc. by operating thekeys K3 and K1, instead of a common battery set. This is a matter ofavailability of sets. This will insert the magneto set MS in place ofthe busy tone source in substantially the same manner as alreadydiscussed with respect to the common battery set CBS. In this case thelocal battery B1 of the magneto set will supply the current for theoperators set MS and this set will not depend upon the supply of currentfrom the battery connected to the A relay.

It will be noted that the closure of keys Kl. and K3 will connect thewinding of relay Z in series with the upper contacts of switch SW andthe windings of relay A which extend to the calling subscriber's set.Relay Z will be operated immediately after any one of the variouseleventh step switches such as SW becomes operated. The relay Z willthen illuminate the lamp L and provide an indication to the attendantthat she has been connected to a party dialing one of the trunks of thelevel which may be in trouble. The attendant in observing the signalwill then notify the calling party or the several calling partiesconnected to the telephone set of the conditions of transmission. Thisis another feature of the invention. The magneto set arrangement MSpermits the attendant to wait until her lamp L has been illuminatedbefore she begins to broadcast to the various calling parties.

in regard to Fig. 1.

set CBS will prevent the calling parties from It will beunde'rstood thatalthough thecircu'it of Fig; 1 has been shown-connected-either to acommon battery set CBSor to a magneto se'tMS, 'both'of thesesetswillnot-be connected simultaneously" in any particularinstallation". Qne or the other will be-used depending on theavailabil-ityof-the' sets, a's-alreadynoted. "Both aresli'own in Figa 1merely to illustrate the possible alternatives available for practicingthe inven tion. 'Althoughthe-arrangement of Fig. 1 illustrates thatthebroaidcasting system-of this invention may be'opera'ted'when theswitchha's been ad-- vancedtothe eleventh step, the invention is.

equally applicable to second selectors; for example; that-have beenadvanced to "a corresponding position; Furthermore, the -common batteryset' CB'SRmay include-indicating means; such as relay Z--' and lampL; orany other'means; to apprizet'h'e attendant that a calling partyhas'beenconnected to the eleventh step i Fig. 2 shows the arrangement of thisinvention applied to a" panel-type of telephone system; The tip, ring,sleeve and hunt conductors T1, R1, S1 and H1, respectively, at the leftconnect to the selector on the district frame shown in the drawings. Thetipand ring conductors T1 and R1 are connected through elements P and Qrespectively of a sequence switch, then through a repeating coil ortransformer T4 and through elements F and G on the sequence switch tothe tip and ring conductors T2 and R2 which are part of-a trunkextending to the next office or to the final frame.

The contact G is connected to one of the windings of a busy tonetransformer T2 over a circuit which includes condenser L1, interruptercontacts ICI, jack contacts KKI, and the grounded secondary winding oftransformer T2. The upper terminal of the jack contacts KKI may lead toother interrupters such as I02 on other frames in the office. Theseinterrupters should be blocked in the operated position when it is dsired to broadcast to the calling parties.

It will be apparent from the drawings that the various calling partiessets wil1 be connected in common to the overflow circuit of theselector. The common battery set CBS or the magneto set MS may beplugged into the jack KK1 to permit'the operator to broadcast to thecallin parties simultaneously, only one telephone set 'being used forthis purpose, as already pointed out The key K-s connected to thetalking with each other when they are simul. taneously connected to theoverflow circuit. The operator, however, will push key K5 to broadcastto the connected parties. Key Ks associated with magneto set MS willserve a similar p111"- Dose.

tain particular arrangements merely for illustrative purposes, it willbe understood that the general principles of this invention may beapplied to other and Widely varied organizations without departing fromthe spirit of the inven tion and the scope of the appended claims.

What is claimed is:

1. In a telephone system, the combination of a plurality of selectors,each selector having a switch which becomes operated when the selectoris connected to a busy or grounded trunk, a plurality of subscribersdial sets, means for individually connecting each of said subscriberssets to each of said selectors, and means including a telephonetransmitter for broadcasting over par- While this invention has beenshown in cer-' allele-paths extending through the operated switches ofisaid selectors to all of; thesubscr b rs sets's m l a w y- 11x; .o

2. In a telephone system, the combination of a plurality oi selectors, apluralityzot subscribers dial sets each of which may be connected'to oneof sa id selectors, a plurality of switches each 0t which is associatedwith one of said selectors,

' means responsive to the dialing by said subaddition; means forindicating the operation of any of the switches associated with saidselectors.

r 4. In a telephone system, the combination of a ura ity s t eac ha n ane enth step switch which becomes operated when the selector isconnectedtqa busy or grounded trunk, a plurality of subscribers dialsets each of which may be connected to oneiof said selectors, atelephone set, and means for connecting said telephone "set through allof the operated switches to enable jan attendant to broadcastsimultaneously to all subscribers sets. t 5. Inca telephone system, thecombination of a plurality of selectors, each selector having a a switchwhich becomes operated when the. selector is connected to a busy orgrounded trunk, a plurality of telephone dial sets each of which may: beconnected to one of said selectors, a. tel-. ephone transmitter, meansfor indicating the op.- erationlofone or more of said s'witches, and

meanslto broadcast from said telephone transmittenthrough the operatedswitches to all sub scribers connected to selectors having operatedswitches. p a t v CHARLES S. RHOADS.

